Abstract Problematic alcohol and drug use confers risk for suicidal behavior and poses special challenges for intervention including increased risk during alcohol use occasions, rapid escalation in suicidal thoughts while consuming alcohol, alcohol and drug use leading to depressive symptoms and interpersonal life events that increase risk, and vulnerability to suicidal behavior following lapses to substance use. Individuals hospitalized for an attempt including those with problematic alcohol or drug use are at marked risk for reattempt and eventual suicide, underscoring the importance of intervention. Hospitalization also represents a ?teachable moment? when interventions may be especially effective. The current 3-year, Stage 1 treatment development study seeks to adapt a brief evidence-based outpatient intervention, the Attempted Suicide Short Intervention Program (ASSIP), for administration in hospital with suicide attempters that screen positive for alcohol or drug use problems. The specific aims are to develop and refine procedures to address problematic alcohol and drug use and that can be administered during hospitalization, leading to the development of ASSIP to address alcohol and drug use, ASSIP-ADU (aim 1); develop and test procedures for training therapists to conduct ASSIP-ADU (aim 2); assess, in an open trial, the feasibility of implementing this intervention (aim 3); 4) conduct a pilot randomized controlled trial (RCT) that compares ASSIP-ADU to a safety procedures? control condition, with both groups receiving treatment as usual (aim 4); and to explore potential mechanisms of the adapted intervention (exploratory aim). This 3-year R34 treatment development application is in response to PA-16-073, Behavioral & Integrative Treatment Development Program sponsored by NIAAA. The research team is experienced studying suicidal behavior, has received training in the original ASSIP intervention by its developers, and has completed a pilot study that established the feasibility of recruitment. Results will set the stage for an adequately powered R01 application to test the efficacy of ASSIP-ADU to prevent suicide reattempt in problem alcohol or drug users.